TPFDF should provide DBDEF user exits for invocation during the PACK operation.

TPFUG_Req_Number: DF00179
Contact Originator Id: claudio.jorge@eds.com
Abstract: TPFDF should provide user exits to be used during the pack process
Description: As each logical record is retrieved on the 'from' or input side of the file, TPFDF should check for a user exit in the DBDEF. If present, the code should be invoked with the option of returning to one of several branch vectors. Each branch point would result in a different action. For example, one branch would continue with a normal pack, another would skip the current logical record but continue and a third could stop the pack at that point and discard the rest of the data and lastly one would stop the pack and keep the rest of the data.
Critical Success Factors: The solution should be generic enough to fit the needs of a variety of contingency situation, e.g. emergency pack to decrease the size of the database, or to replace the existing chains with new pool addresses etc.
Alternative Solutions: It is possible to write applications code that can achieve same the results. However, each application would have to code, test, debug the solutions for many cases and also require driver and controller code to manage the process. This is needless duplication of effort, when TPFDF already has built-in capabilities.
Solution Considerations: There are several aspects to this requirement. The most critical is to provide logical record level exits to be used to keep or dispose of logical records and to continue or terminate the pack. Additional exits are possible, for example: At the start of PACK, (e.g. to turn on the new pool bit or turn on VFA candidacy or to switch to an alternative DBDEF version), at the point where each from block is retrieved (e.g. to set up header specific information), and finally at the end of Pack, (e.g. to turn off the new pool bit). Sample code that might be executed in a user exit could look like.

#IF TM WS02IN1,#WS02SPLT,ON INACTIVE RECORD?
L R14,CE1CR0 POINT TO RECORD
XC STDFCH(4),STDFCH CLEAR FORWARD CHAIN
B 4(,R6) TERMINATE THE PACK #ELSE
B 0(,R6) CONTINUE WITH THE PACK
#EIF

These exits can be made executable only by Utility code (e.g. ZUDFM or CRUISE) or be available even for PACKS triggered by user transactions. This could also be a DBDEF or API command line option e.g. DBCLS REF=…,PACK,CHECKEXIT=YES.